Massage mechanisms for seats are typically built as flexible structures, attached to the seat frame by springs, elastic straps, or other flexible elements.
Prior inventions provide many solutions for massage seat systems.
One solution is to build a sliding frame mounted on rails and electrically actuated up and down along these rails. The moving frame is provided with rollers that press out from inside the back cover of the seat.
The solution is not particularly efficient because of the size, weight and shape complexity of the frame, which prevent the mechanism from acquiring a satisfactory stroke length. Usually, the rollers and frame move back and forth with a span no bigger than a few inches.
Another solution for massage mechanisms for seats consists of a gearbox actuating two chains or timing belts, symmetrically opposite with respect to the gearbox location. The movement of the chains directs the up and down trajectory of a roller feature, traveling along the interior of the seat back.
The solution is unsatisfactory because of the complexity of the entire construction, as well as the weight, high cost and short stroke mechanism.